Dendritic cells (DC) are antigen-presenting cells (APC) involved in the initiation of primary immune responses. Their functions vary with maturation. Immature DC are very effective in processing native protein antigens but lack sufficient cell surface MHC class II and co-stimulatory molecules for antigen presentation. Mature DC are less able to capture new proteins for presentation but are more efficient in the stimulation of resting CD4 and CD8 T lymphocytes. Morphologically, mature DC increase in cell size and granularity. Mature DC have increased levels of cell surface molecules MHC II, CD40, CD83 and co-stimulatory molecules CD80 and CD86. Activation of mature DC results in the synthesis of high levels of IL-12 that enhance both innate and acquired immunity.
Synthetic oligonucleotides are polyanionic sequences. Synthetic oligonucleotides are reported that bind selectively to nucleic acids, to specific cellular proteins, to specific nuclear proteins or to specific cell surface receptors. Synthetic phosphorothioate oligonucleotides of 8 to 100 bases containing a least one unmethylated CpG dinucleotide have been shown to stimulate the immune system (U.S. Pat. No. 6,239,116). In particular, synthetic phosphorothioate oligonucleotides containing a CpG motif (5′purine-purine-Cytosine-Guanine-pyrimidine-pyrimidine3′) have been found to stimulate the synthesis of cytokines such as IL-6, IL-12, IFN-gamma, TNF-alpha, and GM-CSF, the lytic activity of natural killer cells and the proliferation of B lymphocytes (Krieg, Annu. Rev. Immunol. 2002, 20:709-760). Synthetic phosphorothioate oligonucleotides including a CpG motif wherein the number of bases is greater than 14 have been reported to trigger maturation and activation of dendritic cells: increase in cell size and granularity; synthesis of IL-12; increase in endocytosis; and, up-regulation of cell surface molecules MHC II, CD40, CD80, CD83 and CD86 (Sparwasser et al. Eur. J. Immunol. 1998, 28:2045-205; Hartman et al. Proc. Natl. Acad. Sci. USA 1999, 96:9305-9310; Askew et al. J. Immunol. 2000, 165:6889-6895). Synthetic phosphodiester oligonucleotides including a CpG motif wherein the number of bases is 30 have been reported to stimulate the synthesis of IFN and to up-regulate the expression of CD80 and CD86 on DC precursors (Kadowaski et al. J. Immunol. 2001 166:2291-2295).
We have previously described a composition comprising a 2 to 20 base 3′-OH, 5 ′-OH synthetic oligonucleotide selected from the group consisting of (GxTy)n, (TyGx)n, a(GxTy)n, a(TyGx)n, (GxTy)nb, (TyGx)nb, a(GxTy)nb, and a(TyGx)nb, wherein x and y is an integer between 1 and 7, n is an integer between 1 and 12, a and b are one or more As, Cs, Gs or Ts, wherein the oligonucleotide is between 2 and 20 bases. These compositions induce a response selected from the group consisting of induction of cell cycle arrest, inhibition of proliferation, induction of caspase activation, induction of apoptosis and stimulation of cytokine synthesis by monocytes and peripheral blood mononuclear cells (see PCT Publication No. WO 01/44465).
What is needed are new oligonucleotide compositions and methods for using these compositions to modulate the function of immune cells, including dendritic cells.